Wip solr upgrade

CiteSeerX uses Solr 1.3 as index engine which is quite old. We want to upgrade to Solr 4.x which supports many new features. However, the indexed data of Solr 1.3 is incompatible with later Solr. Also, we want to use the new SolrJ API to access Solr and therefore CiteSeerX code must be modified.

http://pychuang-blog.logdown.com/posts/230677-upgrade-solr-for-citeseerx